Mass Spectrometric and Thermodynamic Study of Gaseous Transition Metal (II) Halides

Mass spectrometric and Knudsen effusion techniques have been used to study the vaporization of several transition metal (II) halides. The systems studied include FeI2 and the chlorides and bromides of Cr, Mn, Co, and Ni. The over-all temperature range was between 440 and 700°C. For all systems the monomer is the major vapor species in the temperature range studied. Dimeric species have also been detected in the vapor phase for all systems, except NiCl2 and NiBr2. Vapor pressure data have been combined with mass spectrometric and entropy data to give heats for the dimerization reaction, 2MX2 (g)=M2X4 (g).